Breakfast:

Lunch:

bagel, nonfat yogurt, pretzels, diet soda

Snack:

energy bar, apple

Dinner:

salad with nonfat dressing, pasta in tomato sauce, bread

Dessert:

nonfat cookies, frozen yogurt

Or, maybe you've been experiencing any or all of these scenarios: dozing at your desk in the afternoon, having those nagging hunger pangs between meals, fantasizing about pizza and cookies, feeling sluggish during long workouts.

Not having enough fats in your diet could do you more harm than good.

But I Thought Carbs Were Good for Me?

Carbohydrates are good for us, and we need plenty of them—about 45%-65% of our total caloric intake. In fact, carbohydrate is the muscles' preferred energy source during endurance exercise, which is why it is essential to eat carbs.

But to maximize endurance, sports nutritionists advise that such a carbohydrate-rich diet should not be devoid of
fat. In a study of trained runners, researchers at the University of Buffalo in New York came to a similar conclusion. After spending one month on each of three diets dubbed low-, medium-, and high-fat, runners worked out significantly longer before exhaustion set in when eating the medium-fat diet as compared with the low-fat diet. Athletes on the high-fat diet did not see any greater benefit.

In this study, the low- and medium-fat diets contained about 16% and 31% of calories from fat, respectively. Two main factors contributed to the enhanced endurance seen with the medium-fat diet—total calories and the fat itself.

Calories=Energy=Endurance

A restrictive diet is unable to properly supply endurance athletes with the energy they need to perform. Eating foods that contain fat is one way for athletes to meet their energy needs and improve performance.

During the low-fat diet phase of the Buffalo study, athletes not only ate less fat, they also consumed almost 20% fewer total calories than during the medium-fat phase.

Fat to Fuel Muscles

While hard-working muscles are hungry for the calories that fat provides, they are also hungry for the fat itself. Through training, we improve our muscles' abilities to burn fat. As fitness increases, we still burn more carbohydrate than fat, but fat plays more of a role, both by providing energy and, perhaps more importantly, by conserving precious carbohydrate stores for that big hill coming up at mile 20.

The high-pretzel, low-peanut diets that most fat avoiders are proud of may be leaving them short on muscle-bound fat, forcing the body to depend solely on quickly depleted carbohydrate stores. Essentially, the more intramuscular fat we have to draw on, the longer we can exercise before exhaustion sets in.

Eating Fat Without Getting Fat

We will only gain weight if we consume more calories—regardless of the food package they come in—than we expend. Actually, many of us who shun fat may not be eating enough calories to meet our high energy needs; by adding a little fat, we will increase our calorie intake to where it should be. This is what researchers theorized was the case in the Buffalo study, since athletes did not gain weight when they consumed the medium-fat diet.

By allowing a little fat onto our plates, we may also find that those nagging hunger pangs subside. Fat-restricted diets also tend to be low in protein, which, like fat, induces satiety.

Choose Your Fats Wisely

While we need fats to provide calories, certain fat-soluble vitamins (especially vitamin E), and essential fatty acids, we are also aware that all fats are not created equal. The key is balance.

The Dietary Guidelines for Americans 2010 suggest the following total fat intake as defined by the percentage of your total calorie needs:

Age Group

Total Fat Limits

Children aged 1-3 years old

30%-40% of total calories

Children and teens aged 4-18 years old

25%-35% of total calories

Adults aged 19 and older

20%-35% of total calories

Since trans fatty acids are the most damaging to the heart, athletes should limit their intake of the following:

Fried foods

Margarine

Other foods with hydrogenated oils

Saturated fats such as that found in beef and milk may not be as harmful as once thought. Conversely, monounsaturated fats (found in olive oil and canola oil) have increasingly shown their value in promoting health. Polyunsaturated fats are also thought to be healthy. Foods that contain polyunsaturated fats include the following:

Nuts

Natural peanut butter

Seeds

Olives

Avocados

Fatty fish

Overcoming Your Phobia

A fat phobia can be difficult to overcome, so start with small steps:

Top your salad with low-fat dressing instead of nonfat dressing.

Spread some peanut butter on an otherwise naked bagel or piece of toast or on fruits and vegetables like apples, bananas, and celery.

US Department of Agriculture, US Department of Health and Human Services. Dietary Guidelines for Americans 2010. Available at: http://health.gov/dietaryguidelines/dga2010/dietaryguidelines2010.pdf. Accessed October 14, 2014.

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